There are many design issues that people usually experience during of rotational molding design. However, with the right education and direction, you can easily avoid these issues. The key thing you should note is that you these issues can lead to quality and manufacturing problems. In this article, we'll go through the different issues that are usually experienced.

Flat Walls

This is one of the most common issues that affects rotationally molded product design. It's not easy to create long or large flat surfaces by using the rotomolding process. Basically, the process involves creating a hollow vessel, implying that the parts don't really have an internal structure. Professionals that are experienced usually understand the steps to take to avoid large or long flat surfaces from trying to break. One of the things they do is to incorporate some geometry or structure to the product, and to achieve this, they usually corporate logo, crown, kiss-offs, and even add ribs to the surface.

One of the key things to note is that the tolerance of the rotomolding process is placed at 1%. However, there are cases where a molder can hold a tighter level of tolerance in many ways. Cooling, warpage, shrinkage and other environmental factors are the variables that mostly affect the molded product. Therefore, it's advisable to take all of these into consideration, especially at the beginning of the rotational molding process.

Material Flow

Rotational molding process is different from other processes in many ways, and one of the most obvious differences is that in rotational molding, all the raw materials are first pulverized into a fine powder. On the other hand, other processes mostly make use of a film or pellet. Rotational molding process is grouped into different smaller processes, and one of this is the cook cycle, during which air is collected in between the polymer particles that are subjected to heat. The aim of this is to cook out air as much as possible.

Since the powder materials are rotated, it's vital to ensure that their flow property is within the mold during the rotomolding process. When the materials bridge between the wall surfaces, it can lead to serious issues along the production process. This is a problem that should be discovered quickly during the design process. It's worth noting that beginner engineers usually have a higher tendency to miss out the physical properties that can make materials to web or bridge between the surface of the wall, and this can alter the flow of materials through them. The end result of this is that a void will be created in the areas of the product that is rotomolded.

The best way to avoid this type of issue is to the wall thickness at a minimum of 5 times between the ribs, surfaces, or walls so that there won't be any form of flow problems in them.

Sharp Corners

This is a common production issue, even with other processes, and it's not restricted to rotational molding processes alone. The need to avoid sharp corners during the different stages of the rotational molding design cannot be overemphasized. The main thing to have in mind is that sharp edges tend to reduce the flow ability of the material in the mold. This reduced flow ability will create voids, as shown earlier, and with that, areas are likely to become sharp since they are not properly filled. Another thing to note is that sharp corners also cause the product to have stress rises, and this causes failure or fatigue.

Another thing to note about sharp corners is that they can cause heat sinks to develop in the product, and this results in the build-up of heat in the mold.

Draft Angles

This is a very critical feature of rotational molding design, as it influences the success of the rotomolded product. It's a feature that helps in releasing various parts of the product from the mold, especially during the cooling process. Engraved features like logos, gallon markers and warning plates, heavy textures, and geometry usually need extra draft angles during the design process. Another key thing to have in mind is that engraved textures can work fine even if it's only 3 degrees of draft angle. On the other hand, undercuts will need up to 5 degrees of the draft.

Aesthetics

One of the benefits of the rotational molding design process is that it's vital for ensuring that the aesthetics of the final product that is created is up to expectations. However, aesthetic repeatability is easy that needs to be addressed as fast as possible. Another important thing is for the fixture or mold to be designed carefully, and this should be with aesthetics in mind. During the design phase, the final aesthetics of the product should be put into consideration as well.